As an example of conventional typical work for which a wheel loader is used frequently, V-shape loading will be described. The V-shape loading refers to repetition of loading by moving between a mountain of dirt or gravel and a dump truck while making a V-shaped trail. In this case, the wheel loader repeats forward and backward travel and repeats excavation and discharge and therefore fuel consumption increases in acceleration. Not only that, overheating of a brake due to increase in a load on the brake in deceleration as well as high maintenance cost due to wear of the brake are problems.
Therefore, in Patent Literature 1, an electric motor capable of transmitting torque to driving wheels and an electricity storage means for receiving and transferring electric energy from and to the electric motor are provided and a controller controls electricity generation actuation of the electric motor for receiving torque transmission from the driving wheels and generating electricity during decelerating operation of a vehicle and stores the generated electric energy in the electricity storage means. In other words, the electric motor carries out regenerative braking during the decelerating operation of the vehicle, converts kinetic energy of the vehicle into electric energy, and stores the electric energy. Therefore, it is possible to reduce frequency of use of the brake for the purpose of deceleration to thereby not only suppress the overheating of the brake but also reduce the maintenance cost due to the wear of the brake. Moreover, assist operation for receiving the electric energy stored in the electricity storage means and transmitting the torque to the driving wheels is carried out during accelerating operation of the vehicle and therefore it is possible not only to increase accelerating performance of the vehicle but also to reduce fuel consumption by suppressing output of the engine.